Can I change the view(pan/rotate) while performing an action?
You can't move the 3D view while editing something, even with a 3D mouse, at least in Blender 2.67b, from what I know.
For your &quot;snapping&quot; problem, I suggest you the use of the 3D cursor, by doing the following:

place the 3D cursor at the exact point you want your vertex's final position (with left click in the view, or directly by entering the coordinates in the properties panel - shortcut N - or with the snap menu, see below)
select your vertex
hit shift S to display the &quot;snap&quot; menu
choose &quot;Selection to cursor&quot;


You'll notice that there is also &quot;Cursor to selected&quot; option available in this menu, allowing you to position the 3D cursor accurately at the selection's position.
Hope this helps.